Htjgh rodman



' H. RODMAN. METHOD OF CFSE HARDENING.

APPLICATION FILED MAYIB. 1920.

2 41 6. Patnted Oct. 17, 1922.

FIG. 1.

W!TN E$SE.SS INVENTOR I g ATTORNEYS Patented Oct. 17, 1922,

- UNITED STATES "PATENT OFFICE.

HUGH RODMAN, OF OAKMONT, PENNSYLVANIA, ASSIGNOR TO RODMAN CHEMICAL COMPANY.

METHOD or CASEHARIDENING.

Application filed May 18,

new and improved method of utilizing certain casehardening materials, and simulta neously manufacturing therefrom a case-' hardening material of. diflerent form and characteristics.

The accompanying drawing, wherein Fig. 1 represents a plan view and Fig. 2 a central vertical section, illustrates an ordinary form of carbonizing box packed with parts to be carbonized, and illustrates the distribution of material hereinafter set forth. It will be understood that the form of box, and the parts being treated are in no sense a part of this invention, and the drawing is filed merely by way of illustration. In it there is illustrated a round carbonizing box having aside wall 8, a bottom4, a supporting flange 5, a flange 6, and adapted to be closed by a cover or plate 7. These boxes may be of any desired shape or size, and are ordinarily rectangular. They are made of cast iron, or other suitable substance capable of withstanding heat of a carbonizing furnace. In this box the powdered uncoked coking material 8 is packed for a depth of'a few inches from the bot tom, then this is covered with a layer 9 of granular coked, or noncoked carbonizing' material, resting upon the powdered material. Then a gear 10, to be carbonized is placed on this granular material, and covered over with some granular material to a suitable depth, then additional gears 11, 12, and-13, for example, are placed upon additional layers of the granular material and the last gear is covered over with the granular noncoking material to fill the box.

The cover 7 is then sealed on witha lutingto-thesteel is concerned and which 1s also 14 of fire clay.

To make the invention clear to those skilled in the art, the method of casehardening in common use will first be described. This consists in packing the finished steel parts to be casehardened, together withthe casehardening material (packed about 5.5 the steel surfaces), in an iron box and then,

1920. Serial No. 382,361.

after sealing the box so as to keep out furnace gases, placing it in a red hotfurnace for a period of several hours, during which time the surface of the steel articles absorbs enoughcarbon from the casehardening ma terial to render it susceptible to subsequent hardening and tempering processes. lVhen the boxes'have been sufficiently long in the furnacethey are taken out and ordinarily allowed to cool before being opened, the steel parts being then reheated for hardening, while the casehardening material is saved for reuse.

Tofacilitate close packing of the case'- hardening material about the steel surfaces.

as well as for the purpose of giving efiicient support to-the steel articles, the casehardening material is ordinarily manufactured in the form of small granular fragments or pellets of carbonaceous. material, with which may be mixed or incorporated various energizing chemicals, such as lime or carbonates of sodium or barium.

The usual method of packing is first to place about an inch or two inches of the granular casehardening material in the bottom of a box, and'with this as avbase, to pack the steel articles and granular casehardening material together above the bottom filling just mentioned until the box has been filled to within one or two inches of the top. The remaining one or two inches at the top of the box is then filled in with casehardening material alone. Occasionally this base and top layer of material (in which no steel is embedded) consists of spent or partly spent casehardening material, the idea being that these two layers are mainly for protection of the steel and activecasehardening material in the central. portions of the boxes, and therefore to be filled up as cheaply as possible.

The foregoing is, briefly, the usual method of packing casehardening material in practice. I will proceed to describe a material which has exceptional merit as a casehardening material so far as the transfer ofcarbon very cheap;--but which has not been heretofore successfully used 1n the ordinary packing practice because of certain ditlicultiess accomplish exceptionally rapid and eflicient casehardening at low cost, and at the same time produces a material adapted to be made into the ordinary granular material.

When a good grade of coking coal, or other strongly coking material, is mixed with appropriate amounts of chemical energizers, both ingredients being in crushed or powdered condition, and this mixture is used for casehardening, a deep and satisfactory carbonization is obtained under ordinary conditions of temperature and time of exposure. The rate of carbonization and of penetration of the carbon case is more rapid than where the ordinary granular material is used. The carbonizing materialitself, however, is formed into a unitary mass of coke and it is difficult to withdraw the metal parts from the coked mass. Sometimes the metal may even be warped by the change of position occuring in the solidified,-

coked mass. For this reason such coking mixtures are not satisfactory for general casehardening, although the raw materials are cheap, the preparation of the mixed material very simple, and the chemical action considered alone is excellent. Another reason why such raw mixtures have not been considered available for use in actual casehardening is the fact that some mixtures of coking material and energizing material are not practicable as packing material for direct casehardening for the reason that some raw materials produce a rough surface upon the metal parts during their first heating. But when such raw mixtures have been coked by a preliminary heating, and crushed to appropriate size, the resulting material may be used without danger of roughening the steel surfaces. I have received a patent upon the method of producing casehardening material by mixing coking coal, or other strongly coking materials, with appropriate amounts of chemical energizers, heating this mixture, and then crushing and screening the resulting mass of compound coke to secure casehardening material of commercial form, this being generally about the size of corn or wheat grains. See U. S. Patent No. sea ers, Feb. 15th, 19-10.

I have discovered that the mixture of coking material and chemical energizer above referred to may be economically and efficiently used during the actual casehardening operation by packing the mixture in the bot-tom of the casehardening box (and pos-' sibly in other parts of the box in which the steel parts are not also packed) so that dur ing the first casehardening heat the layer of raw mixture in the bottom of the box will coke and form a mass of compound coke, from which casehardening material of excellent quality and in the granular form preferred in commerce may be obtained by means of a simple crushing and screenin operation. By this method of operation I obtain better and quicker casehardening re sults than where the crushed compound coke (or other commercial casehardening material) is used alone as packing material. That is, by using this method of operation, I obtain the very rapid rate of carbonization which a mixture of coking coal and energizer gives, but which cannot ordinarily be utilized because of mechanical dilficulties. This rapid carbonizing effect follows, I believe, because, while the metal parts are supported by the intermediate packing of granular material which is already coked and therefore now non-coking, the gases produced by the raw mixture of coking coal and energizers in the bottom of the box rise through the packing of steel parts and granular material in the middle portion of the box and bring about nearly as rapid carbonizat on as would have been obtained from using the raw mixture alone throughout.

The raw mixture at the bottom of the box is converted into a mass of compound coke, the energizing chemicals and carbon being held in intimate relation throughout. This mass, when crushed and screened produces the ordinary granular material used in prior practice.

By this invention, then, I derive the following advantages: First, I make immediate use of an exceedingly cheap casehardening mixture which cannot ordinarily be used because of mechanical difiiculties until after a preliminary coking operation. Second, I secure more rapid carbonization than can usually be obtained from previously coked or charred materials. Third, I automatically supply a quantity of masses of compound coke, from which the normal supply of granular packing material may be obtained bya simple crushing and screening operation, such as is well known in the art. Fourth, I make use of a portion of the carbonizing box which is now wasted-in fact in which valuable material is frequently in effect wasted also-and that without sacrifice of any thing of value in the present method of packing. Fifth, I obtain a valuable casehardening result from the use of coking mixtures containing materials which would roughen the surface of steel if packed with it in the raw condition, but Which give smooth surfaces after being once coked and crushed.

A suitable mixture for the bottom layer in the boxes, as described, consists of one hundred parts of coking coal, such as a good grade of Gonnellsville coking coal, as free as possible from ash and sulphur and ground to pass a screen having twenty meshes to the linear inch. ten parts of soda ash and fifteen parts of slaked -lime, the

energizing chemicals being finely ground and thoroughly mixed with the coal. To prevent dust flying in the raw stata'the' mixture may be oiled with about five per "cent of fuel oil or other cheap oil, thoroughly mixed with the other ingredients. Other energizing chemicals may be used, and other subsequently used as packing material;

for instance, the fifteen parts of slaked lime may be replaced with twenty parts of finely powdered limestone.

A further advantage found in this method is that the gases given off by the layer of coking material in the bottom of the box not only serve to increase the speed of carboni'zatlon of the steel parts packed in granular material above it, but that, these gases then pass out of the casehardening box and serve as useful fuel in the furnace. Instead of wasting thesegases, as occurs where casehardening materials of this sort are separately manufactured and then sold to the user, as has been the practice heretofore, they serve this double purpose. The labor and heating, of coking, etc., which have formed a considerable portion of the cost of manufacturing these compound cokes in a separate factory, may be done without extra cost and with substantial advantage in the users factory, by practicing the method herein disclosed.

What I claim is:

1. The method of carbonizing metal parts, comprising the packing in the bottom of a carbonizing box of a foundation mixture of uncooked coking material, packing the parts to be treated in a non-coking material above the said foundation, and heating the box and its contents to suitable oarbonizing temperature.

2. The method of carbonizing metal parts, comprising the partial filling of a suitable container with a foundation mixture of run coked coking carbonaceous material, the

, ackin of the metal arts in ranular coked P a p s carbonaceous material above the said foundation, the closing of the receptacle, and the heating of the whole to suitable carbonizing temperature.

3. The method of oarbonizing metal parts, which consists in packing a suitable container with a foundation mixture of uncoked carbonaceous material mixed with suitable chemical energizing material, packmixed with suitable chemical energizing material, the packing of the metal parts to be treated in granular col-red carbonaceous ma,- terial above the foundation mixture of raw material, the closing of the box, and the subjecting of the whole to suitable carbonizing temperature.

5. The method of carbonizing metal parts and simultaneously manufacturing a carboniz'ing material for dry packing, comprising the placing in the bottom of a suitable container of a foundation mixture of pulverized uncoked coking carbonaceous mate rial mixed with a chemical energizing material, and the packing-of metal parts to be treated above this foundation mixture and surrounded by a non-coking carbonizing material, the closing of the box, the heating .of the whole to carbonizing temperature whereby to carbonize the metal parts and reduce the raw mixture of uncoked carbonaceous material to a unitary mass of coked carbonaceous material containing the chemical energizer, and the subsequent step of crushing and screening the coked mass to form granular coked carbonizing material.

6. The method of carbonizing metal parts, comprising the placing in a suitable carbonizing box of a mixture of finely divided uncoked coking carbonaceous material mixed with finely divided chemical energizing ma terial, the packing in another part of the box of metal parts to be carbonized, the packing around the entire surface of the metal parts of a granular material, and the heating of the whole to carbonizing temperature.

7 The method of dry packing metal parts to be carbonized, comprising the placing of a mixture of uncoked coking carbonaceous material. mixed with suitable chemical energizing material in one portion of a carbonizing box, and the packing of metal parts to be treated in another part of the box, the metal parts being entirely surrounded on all of their surfaces with granular noncoking carbonaceous material.

8. The method of manufacturing coked carbonizing material from uncoked coking carbonaceous material. comprising the packing into a carbonizing box of a mixture of powdered uncoked coking carbonaceous material and powdered chemical energizing material. and the packing into another portion of the box of metal parts to be carbonized, and surrounding the metal parts to be carbonized with granular material to prevent contact of the metal surfaces with the coking carbonaceous material, and the subsequent heating of the whole to oarbonizing temperature.

9. The method of manufacturing granular coked carbonizing material, comprising the placing of a mixture of powdered uncoked coking carbonaceous material and powdered chemical energizing material in one portion of a carbonizing boa the pack ing of metal parts to be carbonized in another portion of the box, entirely enveloping the metal parts to he treated in a granular noncoking material, the heating of the Whole to carbonizing temperature whereby to carbonlze the metal parts and reduce the powdered carbonaceous material to a mass 10 of compound coke containing the chemical energizer, and the subsequent step of crushing the mass of compound coke and screening it to granular size. y

In testimony whereof, I have hereunto set my hand. I

HUGH RODMAN.

. Witnesses:

T. C. MGGHEE, Jo. BAILY BROWN. 

